1. Field of the Invention
The invention pertains to the transmission and reception of base-band or subnanosecond signals relative to reflecting objects and more particularly pertans to means for utilizing object-reflected signals for generation of signals according to the presence of such reflecting objects and also to means for utilizing the reflected signals for generating signals according to the ranges of such reflecting objects.
2. Description of the Prior Art
In prior art object detection and ranging systems, it is common practice to irradiate a distant object with pulses of electromagnetic energy containing many high frequency cycles, and to determine the presence of such an object and its distance from the object detection system as a function of the time interval between the envelopes of corresponding transmitted and received pulses. Although the transmitted pulses are relatively short, they are highly energetic and means must be provided fully to block the receiver for an appreciable time such as, for instance, for one microsecond, precluding the reception of echo pulses until after the transmitted pulse has decayed. In the case of an object detection system employing one microsecond duration transmitted pulses, the receiver is fully blocked for slightly ever one microsecond, rendering the receiver insensitive to objects closer than, say, several hundred feet. Because such prior art transmitters use high level pulse transmission, they also have the undesired feature of rendering a considerable portion of the high frequency spectrum useless for communication and other desirable purposes.
Furthermore, conventional object detector transmitter and reception are notoriously complex and inefficient and are sensitive to many failure possibilities. In the receiver, complex frequency control and conversion arrangements are required as well as intricately designed and expensive receiver gain elements, each of band widths sufficient to process the reflected pulse signals. There is not known in the prior art a radio frequency object detector system which may be successfully operated over substantial object distances in a wave band already allotted to conventional receivers in the same geographical vicinity. More particularly, there is not known in the prior art a radio frequency object detector system of the just described type which can operate at very low or legal power levels in such wave bands without it itself being the victim of intolerable interference. Furthermore, there is not known in the prior art a radio frequency object detector system such as described in the foregoing and also capable of transmission and reception of signals having an extremely wide frequency spectrum without interfering with the transmission of ordinary radio communication signals.